The present invention relates to a dynamically working umbilical or control cable string, intended to hang in a catenary form between a connection point on the seabed and a connection point located on the surface and which may be attached to a floating structure, which umbilical is of the type having low weight per running meter and includes flowlines and optionally current conducting cables, all of which are twisted around the longitudinal axis of the conduit and lie in channels in spacers for free axial movement of the cables and flowlines in the said channels.